Movable jet deflector to compensate for destabilizing moment in a jet aircraft



Oct. 5, 1953 JQNAS 2,554,552

J. MOVABLE JET DEFLECTOR TO COMPENSATE FOR DESTABILIZING MOMENT IN A JET AIRCRAFT 3 Sheets-Sheet 1 Filed Feb. 24, 1948 INVENTOR. By Jul I05 L/b/VAS Oct. 6, 1953 2,654,552

J. JONAS MOVABLE JET DEFLECTOR TO COMPENSATE FOR DESTABILIZING MOMENT IN A JET AIRCRAFT 3 Sheets-Sheet 2 Filed Feb. 24, 1948 INVENTOR. BY uuuus Jo/v.45

Oct. 6, 1953 J. JONAS 2,654,552

MOVABLE JET DEFLECTOR TO COMPENSATE FOR DESTABILIZING MOMENT IN A JET AIRCRAFT Filed Feb. 24, 1948 3 Sheets-Sheet 3 Patented Got. 6, 1953 omrso stares FFIQE MOVABLE J ET DEFLEC FOR DESTABILIZIN AIRCRAFT Julius Jonas, Los An Northrop Aircraft,

TOR T COMPENSATE G MOMENT IN A JET geles, Calif, assignor to Inc., Hawthorne, Calif., a

6 Claims.

My invention relates to jet deflectors and more particularly, to a means and method of effecting the deflection of a jet without incurring unsatisfactory flow conditions. This means and method may, for example, be used in conjunction with the deflection of a jet issuing from a turbojet engine.

Many modern airplanes are driven by turbojet engines whose aftward discharging jets produce a forward thrust along the axis of the engine.

In single or multiple jet engine installations, as a rule, the arrangement of the engines is such that the sum of the moments of all thrust forces about the airplanes center of gravity is zero.

In many instances, however, it is not convenient to mount the turbojet engines in the airplane so as to attain a zero moment configuration. Configurational considerations often conspire to make it desirable to displace the jet axes below the horizontal reference plane passing through the C. G. of the airplane, thus producing a destabilizing pitching moment which must be compensated for by additional horizontal tail surface area or increased tail moment arm, resulting in a performance penalty of the airplane.

In such cases, a small deflector vane placed on the nozzle exit of the exhaust pipe-usually on the top portion thereof-can be utilized to deflect the jet to the extent of causing the jet force to pass either through the C. G. of the airplane or as close to it as acceptable from stability and control considerations.

However, when this is done the effective tail pipe area is restricted, and furthermore a back pressure is produced at the base of the deflector, both of these factors upsetting the proper operation of the jet engine.

Accordingly, it is an object of the present invention to provide a means and method of deflecting a jet issuing from a nozzle without causing substantial reduction in the nozzle exit area and without creating any substantial back pressure in the jet.

I have found that such an object can be attained by venting a portion of the jet gas to a region of lower pressure at or near the points where the jet direction is changed. In this case, the deflector causes a deflection of the jet without necessarily restricting the effective tailpipe exit area. Thus, in the case of a turbojet installation the vented deflector, if installed at the end of the tailpipe nozzle, particularly if the nozzle is vented into the atmosphere directly, will permit the deflection of the jet without upsetting engine operation because the effective nozzle exit area can be efiectively controlled by the selection of a proper vent area. It is obvious in this case that the location of the deflector assembly at the end of the tailpipe can be brought about either by mounting it directly on the tailpipe or on surrounding structure.

Again, it has almost become standard procedure to surround the tailpipe with an outer conduit sometimes referred to as a shroud, which extends past the jet nozzle, thus forming the mixing section of a jet pump which aspirates cooling air through the space formed by the shroud and tailpipe thereby keeping the surrounding structure from becoming excessively hot.

When no deflector is used, the jet will properly issue from the exhaust system and aspirate the amount of cooling air commensurate with the design. However, I have found that when a plain deflector is placed at the exit of the outer conduit formed 'by the shroud, extending into the jet issuing from the jet pipe nozzle, suflicient back pressure is produced at the base of the deflector not only to reduce the aspirated cooling flow to zero but also, even in this case, suflicient to cause a partial reversal of the main jet, thereby forcing a portion of the jet to flow back into the annular space formed by the tailpipe and the outer shroud conduit. This not only causes structural overheating, but again upsets the proper operation of the jet engine.

Another object of the present invention is to provide a means and method of providing a substantially uninterrupted secondary flow and unimpeded engine operation, even though the jet is defiected, when a cooling shroud is used around the jet tailpipe.

In as much as there are many instances during airplane control when it may be desirable to change the pitching moment, it may also be desirable to change the pitching moment by changing the angle of jet thrust application. In consequence, I may make the deflector movable to obtain different jet deflection angles. As changing the angle of deflecting surface will change the effective jet exit area it is another object of the present invention to provide a means and method of varying both the jet deflection angle 3 and the vent area to provide a substantially constant eifective jet exit area.

When any considerable amount of jet flow is vented, some thrust is produced by the vented gas. In some cases it may also be desirable to deflect the vented gas and it is still another object of my invention to provide a jet deflector in which substantially all of the jet flow is deflected without substantial reduction of jet exit area.

In broad terms as'to method," the present invention comprises deflecting a jet flow'as it issues from a nozzle, and eliminating adverse back pressure and maintaining substantially full exit areafor the jet, by venting a portionof; the .jettoaregion of lower pressure at t e sweatersaires tional change of the jet occurs.

In broad terms as to apparatus, my invention comprises a jet pipe with a deflector-Wane eater-me ing into the flow issuing tram-tramps? Relief openings are positioned at the base of the deflector to vent some of the fiOTWftO, preyentithe? build-up of adverse back pressures in that region.

My invention can be more readily understood by reference to the following description of a preferred: embodiment thereof; and tothe accom panying drawings in which i Figure; l is a; diagram; representative of the prior art, of aijet: nozzle exhausting into the'- atmosphere;-

Figure 2 is? a? diagram showingthe: attacl'i- 3 ment :of; acjeti' deflecting vane Ito the nozzle of:- Figure 1.

Figure 3- is a: diagram: showing where: backpressure develops at the base of the plain-de fleeting vane;

Figure 4115 a diagram? shcWing gas flow with relief openings at the base ofithe 'deflecting vane.

Figure 5 is an-perspective view of a jet outlet 1 equipped with; one aspect of a deflector: vane? made in accordance-withthe "presentninvention.

EiEUIGP'Gi'iS. a. diagram showingtthe present in-J vention as; applied to a primary. jet positioned to: create'aisecondaryfiow;

Figure 7 is: a long-itudina'hsectional view; part" 1y 'diagrammaticeof a j et: nozzle equipped with: at: 4 5 movable yane.

Figure; 8; is a cross: sectional: view takenas indicated by; line 8-'-8- innFigure. 7;

Figure;9, shows-two diagrams'zillustrating -hove a-: destabilizing moment :caused: by? jet: engine inestallation below the: horizontali reference? plane: passing: through: the: C. 'Gi. of the: airplane can 3 beqcompensated for byrjet-rdeflection:

Figure 10" is a diajgram illustrating;- a-rl'othen embodimentof;the-inventiom Referring first to, the configurationshowrr in 3' Figure- 1; the jeti: pipe I represents -;:for-- example; the tailpipe of a turbojet engine-having: a nozzle: exit area; A- ;A:

If it isdesired' toflowissuing fromv such a: system;; as='v explained; above, I a': deflecting surface; may be; positioned-1 at.=the nozzle exit; as". shown; in: Figure Thedeflector vane may be attached toetheetai'lpipei l ifit is'sufliciently' strong ori to: surrounding structure; 2. Here a deflector vanex 4 cani'ber placed at an angle at tor:the:horizontal-;projecting: intothe jet flow.- selectingra'proper value: of; vane chordlength-L andqvaneangle-many desired-jet deflection angle; 9-. can be obtained so that the centerline 42 0f the jet will haverbeen-i rotated into the proper direction, for-example: to improve longitudinal stability, ;as pointed, out above.

However, Lhave-foimd-thatwhen anyvane:

deflect the: outcomin'gkjet 60 4 angle a. is used in excess of a few degrees, sufficient back pressure is produced at the base of the deflecting surface in the region of point C, as shown in Figure 3, to cause an efiective reduction of nozzle exit area, with consequent reduction of thrust. To overcome this difflculty and still maintain the inherent simplicity of the deflecting surface, I provide a relief opening 5 at region C where the deflection starts, as shown in Figure' hfi If afpropermagnitude of the relief opening 5= is" selected, it is possible to skim off part of the jet to the extent of practically elimiria-ting the adverse back pressure in region C. Yet practicallypall ofthe primary jet is forced to? alongitlfe an'g'le of the deflector surface 4", g1v1r'ig the desired jet deflection without the above mentioned reversal of part of the jet.

In "Figure-5' aperspective view is shown of one form of-aj-te te *dj'flector system embodying the present invention: Here the deflector vane 4 extends,-:0ver:about:one half of the outer conduit 2 periphery, the vane being symmetrically located adout the vertical axis passing through the exhaust opening of the tailpipe. It is approximately: circular with a larger? radius than the conduit.to'tprovide theupper: relief-"opening 5- divided by a": deflector vane supportin'g:stru't '62 It :will be noted that in the device illustrated in Figures 4-'and-:5, that portion of'rthejetwissuingr. through i the vent 1 openings 5:. is: also: deflected: by extending the top half of the conduit 2 above: the combinedflow exit: and givinggthat extension I a downward-angle corresponding to,=the= deflector angle a: Inzthiswaygkthe proper; thrust angle is also obtainedsinrthe"ventrfloywr Thi relatively small flow" does-r not'cause suffieientp back pressure to: interfere with engineyoperations; However, when the vent "flow: is'sti-llPSmal-ler, 'it maybe directed in line with they original-jet, .-or, if larger, it' maybe/deflected;along*with-;the jet with-- additional dividing vanes placed between the deflectingvane= 4; and deflectingextension: 1" to preventiturbulence in the skimmed-off .flow. In'any event-,.a portion'iof the-:jetflow is vented to r the atmosphere adjacent, to the base of. the; main'defiector fvane: p

The, defleetor-- of? the presentinvention: is} equally satisfactory for) installations whereka shroud 2a in used around i-the: primaryjet. pipe. and extended; beyond the end of th jet-pipe tocause: ajetpump, action aspirating a; sec.--- ondary-.-- cooling airflow through as space=v 8 be} tween *the' primary; jet pip e and the shroud. In; thiscase;;thedeflector 4 is? placed onthe end; of the shroud; and ifa plain. deflector were, tobe used a back pressure would be deva pea; sufficient-to: cause a. reversal of. the secondary flow.

In this-instance also, ,the verit 5 placed atth'e'i baseof thedeflectorfass shown inlFigure' 6i, will.

eliminate the reversal ofithej secondary? flow,-

- restore-theproper. exit area]. and permit, proper" engine operation even though the j et' is deflected In this' manner; y. selectionl off the; roper relief opening, the sauce less, ormore secondary? coolingtairflowcana-be obtained with the 'deflectoil as when nodeflector'is'us e'd.

I-- do not wish to be. limited-to; the. application" of my; invention:- to, agfix'ed deflecting? vane be.- cause the -same --results are obtainable-when.the,v deflector vane angleis -adjustable or condensers, as; might be desirableso. as: to} attain .airp' lane controlapart irom use; of airplane control Isu'r; faces forthatvpurpose for example. (fine such. an arrangement is-rshowrr in Figures' 7'. and 8." v

One arrangement that has proved satisfactory for this purpose is shown in Figures 7 and 8.

Here a shroud I is concentrically placed around the tailpipe I and extends beyond it to provide a combined flow exit area BB. In this case, the deflecting vane 4 is of airfoil section and is positioned at the desired angle, the vane being symmetrically located about the vertical axis passing through the exhaust opening of the tailpipe. Vent opening is provided between the leading edge of the deflector and the shroud, and the vent extension I is'extended aft to terminate in substantially the same plane as the trailing edge of the deflector vane 4 to provide a relief duct ll between vane and extension. Extension 1 is curved to deflect the vented flow.

For a normal deflection the vane 4 is preferably positioned along line XX so that the top contour of vane 4 is substantially parallel with the curve of extension 7.

However, as pointed out above, it may be desirable to rotate vane 4 to achieve varying deflection angles. In this case, vane 4 at its lower ends is rotatably attached to shroud m as by pivot pins I 2, and an actuating rod I3 is attached to, for example, the rear third of vane 4 by fitting [4. Rod I3 is actuated by actuator l5 of any convenient type, such as, an electrical screw jack for example. Operation of actuator [5 will move vane 4 on pivot pins l 2 as shown by dotted outline into position Y-Y, for example, thus changing the jet deflection angle. At the same time, the leading edge of vane 4 has moved rearwardly thus increasing vent area 5 to compensate for the decreased effective area below the vane 4. Likewise, movement of the vane upwardly to decrease the deflection angle will reduce the vent area somewhat, but this is not as important, as movement upwardly does not reduce the effective exit area but increases it. I have found that for pitch control purposes it is not necessary to change the angle of the extension I although that also can be accomplished by similar pivoting and control if desired.

It will be clear to those skilled in the art that the embodiment shown in Figures 7 and 8 can be applied either to a straight jet as illustrated in Figure 10, or a jet arranged to create a secondary flow.

In Figure 9, diagrams A and B show the effect of jet deflection in an airplane X having the twin jet engines E symmetrically mounted with their jet axes below the horizontal longitudinal axis passing through the C. G. of the airplane.

In diagram A, no jet deflectors are used, and the jet axis 9' is parallel with the C. G. axis 9. This produces a climbing moment on the airplane as indicated by arrow C. When a deflector assembly D, such as that shown, for example, in Figure 7, is used on each jet exhaust with a deflection angle of from 10-15, as shown in diagram B, the climbing moment will be opposed by a diving moment produced by jet deflection as indicated by opposed arrows 0.

What is claimed is:

1. In an airplane driven by a jet of hot gases directed rearwardly through an exhaust opening of the tailpipe of a gaseous combustion turbine engine, said jet located so as to produce a destabilizing moment on said airplane when in flight, a deflection vane having a basal portion positioned adjacent to and symmetrically located about the vertical axis passing through said exhaust opening to provide a vent for a por tion of said gases between said basal portion and an edge of said opening, the remainder of said vane extending outwardly beyond said opening and toward the axis of said tailpipe to intersect and deflect at least a portion of the gas passing through said opening; said vane being rotatable about a pivot to change the angle of inclination of said vane with respect to the axis of said tailpipe, said vane being positioned with reference to said pivot to increase the vent area with an increased deflection angle of said vane, whereby the deflection of said gases is changed without substantially changing the total effective exit area; said vane having one deflected position creating a moment on said airplane opposed to and substantially compensating for said destabilizing moment; and an extension member projecting rearwardly from the tailpipe opening toward the axis of said tailpipe and spaced from said vane to provide a passage therebetween for the vented gases, said passage being inclined toward the axis of said tailpipe.

2. Apparatus in accordance with claim 1, wherein said edge of said opening is substantially circular, and said basal portion has circular contours of greater radius than that of said edge to provide a vent of crescent shape between said basal portion and the adjacent edge of said pipe nozzle.

3. Apparatus in accordance with claim 1, wherein said edge of said opening is substantially circular, and said basal portion has circular contours of greater radius than that of a said edge to provide a vent of crescent shape between said basal portion and the adjacent edge of said pipe nozzle, and wherein the longitudinal cross section of the vane is in the form of an airfoil section.

4. In an airplane driven by a jet of hot gases directed rearwardly through an exhaust opening of the tailpipe of a gaseous combustion turbine engine, said jet located so as to produce a destabilizing moment on said airplane when in flight, a shroud of substantially circular section concentrically positioned around said tailpipe and open to the atmosphere at an upstream location of said shroud, said shroud extending rearwardly beyond said exhaust opening to create a negative pressure between said shroud and said opening, thereby creating a cooling air flow between said shroud and said tailpipe; a deflector vane mounted near the end of said shroud and extending beyond the opening of said shroud and having a basal portion positioned adjacent to the opening of said shroud to provide a vent for a portion of said gases between said basal portion and the edge of the opening of said shroud, the remainder of said vane extending outwardly beyond the edge of said shroud opening and toward the axis of the tail pipe to intersect and deflect at least a portion of the gas issuing from said exhaust opening; said vane being rotatable about a pivot to change the angle of inclination of said vane with respect to the axis of said tailpipe, said vane being positioned with reference to said pivot to increase the vent area with an increased deflection angle of said vane, whereby the deflection of said gases is changed without substantially changing the total efiective nozzle exit area; said vane having one deflected position such as to create a jet deflection producing a moment on said airplane opposing said destabilizing moment; and an extension member projecting rearwardly from k 2$545i51 1 aidi slrn'cmd itcwardthevaxis: of; said ta'zilmfiesanm spaced frnmsaith vane t'w provide aw passage the-rebetween afowthe'vente d gases said-passage? being: inclined etowanwthe axis-ofi said xtailpi'pei th epath 1 of the. cooling: passing; between- 10'; 2481.33? said-shroud. andtailpipe.

GrAppa-PatuS: accordance withclaim 4', wheremwaidhvme has, circular-- contours imthe same sense as the contour of the -endxedger of said%-shroud-=,bus= With-substantially greater radii- 5 of, cmvafturef C011 pro 'ide.- aw crescent; shaped vent g y and whereinth e longitudinaL cross; section. of 5 75 the: vane is. in the. form of an; airfqil section! JULI-UsiJoNAsz References :emai m1 tfm. fi1e=;of .this-.*patentf UNITED suwms PATENTS Ntme Date" Re'es; Feb. 9; 19263 clr'x'illingworth; Mir; .31; A 19312 Bo'gstrafid NOV. 22,,193'2" Howse A'pr'. 4119441 Myefetal May.- 13; 192%7' N'al Sept? 6, 1949' Gb'dfla'rd Dc. 20;,19491 Bee" A'ug; 15,,1950" FOREIGN PATENTS? Ccrvintfiy" Date Great Britain Sept. 29, 194 7 

